EP0592256A1 - Solid and amorphous alkaline metal silico aluminate - Google Patents

Abstract

The present invention relates to a solid and amorphous alkali metal silicoaluminate, characterised in that it has the following molar chemical composition: xSiO2. yAl2O3. zM2O. wH2O, in which M represents an alkali metal, preferably sodium, x is between 2 and 2.9, y is between 0.8 and 1.2, preferably equal to 1, z is between 0.8 and 1.8 and w is greater than or equal to 5, in that it has a specific surface area of less than 50 m<2>/g, a pore volume of at least 1 cm<3>/g and an oil absorption of at least 170 ml per 100 g of silicoaluminate. It also relates to a detergent composition comprising this silicoaluminate. Finally, it relates to the process for the preparation of this silicoaluminate.

Description

The present invention relates to an amorphous and solid alkali metal silico-aluminate, as well as to the process for its preparation.

It also relates, as an application, to a detergent composition comprising this amorphous and solid silico-aluminate.

Amorphous silico-aluminates have been known products for a long time and are used in particular in the detergency field, as absorption sites for certain components, such as surfactants, optical brighteners and perfumes. This makes it possible to densify the detergent compositions, a characteristic which is particularly sought after today. However, these amorphous silico-aluminates generally do not have a very high cation exchange capacity and very high cation exchange kinetics.

Materials capable of exchanging cations and their use, for example for softening water, are well known in practice. Mention may thus be made of zeolites which have a high calcium exchange power, but a too low magnesium exchange power. These products can also be criticized for not having sufficiently high cation exchange kinetics.

An object of the invention is therefore to propose an amorphous silico-aluminate having an absorption power greater than or equal to that of known amorphous silico-aluminates, as well as an improved capacity and kinetics of calcium and magnesium exchange .

The Applicant has found that this object and others can be achieved by the present invention which in fact relates to an amorphous and solid alkali metal silico-aluminate, characterized in that it has the following molar chemical composition (I):

x SiO2; y Al2O3; z M2O; w H2O,


in which M represents an alkali metal, preferably sodium, x is between 2 and 2.9, preferably between 2 and 2.4. y is between 0.8 and 1.2, preferably is equal to 1, z is between 0.8 and 1.8 and w is greater than or equal to 5, and in that it has a lower specific surface at 50 m2 / g, a pore volume of at least 1 cm3 / g and an oil absorption of at least 170 ml per 100 g of silico-aluminate.

Depending on its water content, the silico-aluminate of the present invention can be in the form of powders or be present in suspension in water (slurry).

Analysis of the silico-aluminates of the present invention by transmission electron microscopy reveals a product in the form of agglomerates themselves made up of submicron particles.

Note that the silico-aluminate of the present invention has cation exchange capacities comparable to those of zeolites in the case of calcium and greater in the case of magnesium, this is in particular due to the chemical composition of the silico-aluminate of the present invention. Thus, its capacity and its exchange kinetics improve when the value of w increases. We therefore prefer a silicoaluminate according to the invention of chemical composition (I) in which w is greater than or equal to 6. The upper limit of w is determined by the shape that we want to give to the amorphous silico-aluminate of the present invention . Thus, in the case of powders, for example, it is within the reach of the skilled person to determine the upper limit of w.

More particularly, the silico-aluminate according to the invention has a calcium exchange capacity of at least 250 mg of calcium carbonate per gram of anhydrous silico-aluminate, a calcium exchange kinetics of at least 200 mg of calcium carbonate per gram of anhydrous silico-aluminate after one minute of contact, a magnesium exchange capacity of at least 120 mg of calcium carbonate per gram of anhydrous silico-aluminate and / or exchange kinetics of magnesium of at least 60 mg of calcium carbonate per gram of anhydrous silico-aluminate after one minute of contact. Preferably, the silico-aluminate according to the invention has a calcium exchange capacity of at least 270 mg of calcium carbonate per gram of anhydrous silico-aluminate, a calcium exchange kinetics of at least 220 mg of calcium carbonate per gram of anhydrous silico-aluminate after one minute of contact, a magnesium exchange capacity of at least 190 mg of calcium carbonate per gram of anhydrous silico-aluminate and / or exchange kinetics of magnesium of at least 65 mg of calcium carbonate per gram of anhydrous silico-aluminate after one minute of contact.

The silico-aluminate of the present invention has, more particularly, a specific surface of between 10 and 20 m2 / g and / or a pore volume of at least 2 cm3 / g, preferably at least 4 cm3 / g.

The silico-aluminate of the present invention has an oil absorption of at least 170 ml / 100 g, and more particularly of at least 190 ml / 100 g. This absorption value is calculated according to standard NF-T45-121 (taking dibutylphthalate).

This characteristic is particularly advantageous for the development of compact detergents comprising in particular a high level of surfactants.

The present invention also relates to a detergent composition comprising in particular as an absorbent and / or sensor for divalent cations of the solid and amorphous alkali metal silico-aluminate as described above. The amount of silico-aluminate according to the invention is generally between 4 and 40% by weight of the detergent composition.

Finally, the present invention relates to a process for the preparation of the solid and amorphous alkali metal silicoaluminate described above, characterized in that it comprises the following stages: (1) mixing of an aqueous solution of alkali metal silicate of ratio molar SiO2 / M2O greater than or equal to 2 and dry extract of between 30 and 50% by weight with an aqueous solution of alkali metal aluminate diluted by addition of alkali metal hydroxide and water, so that the molar composition of the mixture before gelation is as follows:

2-2.9 SiO2; 0 8-1.2 Al2O3; 3-10 M2O; 60-200 H2O;


in which M represents an alkali metal, (2) possible maturing of the gel formed in step (1), (3) filtration or centrifugation, (4) washing, (5) drying of the suspension obtained after step (4 ) and (6) possible grinding of the dried product.

Throughout this process, the preferred alkali metal is sodium.

During step (1), simple stirring, in particular by rotary blade, is sufficient to produce a homogeneous mixture due to the delay in gelation, this delay being due to the depolymerization of the chosen alkali metal silicate.

The mixture before gelation preferably has the following molar composition:

2 SiO2; 0.8-1.2 Al2O3; 4-8 M2O; 60-200 H2O.

Even more preferably, the mixture before gelation has the following molar composition:

2 SiO2; 1 Al2O3; 6 M2O; 120 H2O.

The mixing of the reagents can be carried out in different ways. It is preferred, however, either to introduce the two aqueous solutions in parallel, or to introduce the aqueous solution of alkali metal silicate into the dilute aqueous solution of alkali metal aluminate. This preferred procedure makes it possible to obtain a more homogeneous gelling.

The gel formed during step (1) can then be kept stirring, this corresponds to the possible ripening step. The carrying out of this step (2), as well as its duration generally depend on the whole of the device used to implement the method of the invention.

It is generally carried out at a temperature between 15 and 50 ° C, preferably at a temperature between 15 ° C and 30 ° C.

Following gelation and possible ripening, before or after elimination of the mother liquors (step (3)). one can consider implementing a carbonation of the product obtained. This carbonation has the advantage of being able to possibly eliminate or at least lighten certain stages, such as the washing stage (reduction in the number of washes) or the filtration or centrifugation stage. This carbonation is carried out by addition of carbon dioxide which reacts with the free alkali metal hydroxide. The product thus obtained is in the form of a non-pulverulent powder consisting essentially of silico-aluminate, as described in the present invention, and of alkali metal carbonate monohydrate. This carbonated product can also have significant advantages in detergency by lowering the pH and by providing carbonates.

After gelling and possible ripening, the product obtained is filtered or centrifuged in order to remove the mother liquors, washed to remove in particular the excess of alkali metal hydroxide; this is achieved by any means known per se. In practice, filtration is carried out using a filter press and washing is carried out using demineralized water.

It may also be advantageous to add additives to the suspension (slurry) before the drying step or optionally to the mixture of step (1). By additives is meant water-soluble polymers conventionally used in detergency which in particular have an anti-redeposition effect, such as copolymers of acrylic acid and maleic anhydride or polyacrylates.

Of course, the drying is carried out in a controlled manner so as to obtain a silico-aluminate of molar composition (I). This drying step can be implemented by any means known per se, such as in particular thin layer drying, drying by lyophilization, by microwave or by fluidized bed. Preference is given, however, to spray drying, which is easier to use industrially.

The grinding step can be carried out by any means known per se. It can in particular be carried out by a ball, hammer or air jet mill.

Thus, the average diameter of the particles of the amorphous silico-alulminate obtained by the process of the present invention is between 1 and 100 μm, preferably between 5 and 20 μm.

In what follows and what precedes, the measurement of the calcium exchange capacity is based on the complexometric dosing in return of free calcium by EDTA after elimination of the exchanged silico-aluminate and the result is expressed in mg of carbonate. of calcium fixed per gram of anhydrous silico-aluminate at a time t = 15 min, the amorphous silico-aluminate to be tested being introduced at a concentration of 1 g / l in anhydrous at time t = 0 in a solution of known calcium concentration (0.005 M CaCl 2 solution) at 25 ° C. The measurement of the magnesium exchange capacity is based on a method directly transposed from the previous one.

In what follows and what precedes, the measurement of the calcium exchange kinetics is based on the monitoring of the evolution of the calcium concentration as a function of time in the presence of silico-aluminate to be tested. The electrode used is the electrode "Orion", model 9320. At time t = 0, the silico-aluminate is introduced at a concentration of 1 g / l in anhydrous in a solution whose calcium concentration is 3.0.10⁻³M (buffer pH = 10, 2) at a temperature of 25 ° C; the potential is noted after one minute (the concentrations are then calculated using a calibration curve). The result is therefore expressed in mg of calcium carbonate fixed per gram of anhydrous silico-aluminate after one minute of contact. The measurement of the magnesium exchange kinetics is based on a method directly transposed from the previous one.

In order to illustrate the invention, without however limiting its scope, examples will now be given.

Unless otherwise stated, the percentages are by weight.

EXAMPLE 1

In this example, we use:

A sodium silicate solution with an SiO2 / Na2O molar ratio equal to 2, with a density of 1.55 and a dry extract of 45.7%,

A sodium aluminate solution prepared by attack with sodium hydroxide pellets (at 105 ° C., for 2 hours) of the alumina hydrate sold by Prolabo, to obtain a stock solution containing about 20% of Al2O3 and 18 to 20% Na2O, then by diluting this mother solution with soda and permuted water. Thus, the Al2O3 and Na2O contents are 4.1 and 12.6% respectively.

An adequate quantity of the sodium silicate solution is poured in less than two seconds into the reaction sodium aluminate solution placed, at room temperature, in a reactor stirred by means of an anchor driven at constant speed. The molar composition of the reaction medium before gelling is then as follows:

2 SiO2; 1Al2O3; 6 Na2O; 120 H2O.

The gelation time requires one to two minutes, which allows the two components to be mixed homogeneously. The gel formed is kept stirring, still at room temperature, for 30 minutes. After this ripening step, the mother liquors are separated on a press type filter and is followed by three washes with permuted water. Then the cake obtained is resuspended in deionized water at a rate of 10% solid.

This suspension is then atomized to obtain an amorphous silico-aluminate powder.

Densité tassée:

0,21 g/ml

Diamètre moyen:

12,7 µm

Surface (BET azote):

17 m2/g

Volume poreux:

4,2 cm3/g

Pouvoir absorbant:

200 ml/100g

Extrait sec:

71%

pH (5% sol. aqueuse):

11,1

Capacité calcium:

280 mg CaCO3/g d'anhydre

Cinétique calcium:

218mg CaCO3/g d'anhydre à 1 minute

Capacité magnésium:

195 mg CaCO3/g d'anhydre

Cinétique magnésium:

67 mg CaCO3/g d'anhydre à 1 minute et sa composition molaire est la suivante:
2,38 SiO2; 1 Al2O3; 1,07 Na2O; 7,1 H2O.

This amorphous silico-aluminate has the following characteristics:

Packed density:

0.21 g / ml

Average diameter:

12.7 µm

Area (BET nitrogen):

17 m2 / g

Porous volume:

4.2 cm3 / g

Absorbency:

200 ml / 100g

Dry extract:

71%

pH (5% aqueous sol.):

11.1

Calcium capacity:

280 mg CaCO3 / g anhydrous

Kinetic calcium:

218mg CaCO3 / g anhydrous at 1 minute

Magnesium capacity:

195 mg CaCO3 / g anhydrous

Kinetic magnesium:

67 mg CaCO3 / g anhydrous at 1 minute and its molar composition is as follows:
2.38 SiO2; 1 Al2O3; 1.07 Na2O; 7.1 H2O.

EXAMPLES 2 TO 4

The procedure is exactly as in Example 1, the molar composition of the reaction mixture is therefore the same. the results obtained show the reproducibility of the process. The table below collates the results obtained. Examples 2 3 4 Dry extract (%) 73.2 72.9 65.5 Calcium capacity 293 mg / g 286 mg / g 285 mg / g Kinetic calcium 208 mg / g at 1 min. 220 mg / g at 1 min. Average diameter 11.1 µm 9.0 µm 13.7 µm Porous volume 4.6 cm3 / g 2.3 cm3 / g Absorbency 202 ml / 100g 180 ml / 100g 172 ml / 100g

The silico-aluminate obtained from Example 4 has the following molar chemical composition:

2.25 SiO2: 1 Al2O3: 0.94 Na2O; 8.65 H2O.

Teneur en 4A:

85%

Diamètre moyen:

2 à 5 µm

Capacité calcium:

> 250 mg/g

Cinétique calcium:

150 mg/g à 1 min.

For comparison, the specifications of Procter and Gamble for zeolite 4A are as follows:

4A content:

85%

Average diameter:

2 to 5 µm

Calcium capacity:

> 250 mg / g

Kinetic calcium:

150 mg / g at 1 min.

Claims (18)

1. / Solid and amorphous alkali metal silico-aluminate, characterized in that it has the following molar chemical composition (I):

x SiO2; y Al2O3; z M2O; w H2O,

in which M represents an alkali metal, preferably sodium, x is between 2 and 2.9, preferably between 2 and 2.4, y is between 0.8 and 1.2, preferably is equal to 1 , z is between 0.8 and 1.8 and w is greater than or equal to 5, and in that it has a specific surface area of less than 50 m2 / g, a pore volume of at least 1 cm3 / g and an oil absorption of at least 170 ml per 100 g. 2. / Silico-aluminate according to claim 1, characterized in that it has a chemical composition (I) in which w is greater than or equal to 6. 3. / Silico-aluminate according to one of claims 1 or 2, characterized in that it has a calcium exchange capacity of at least 250 mg of calcium carbonate per gram of anhydrous silico-aluminate, kinetics calcium exchange of at least 200 mg of calcium carbonate per gram of anhydrous silico-aluminate after one minute of contact, a magnesium exchange capacity of at least 120 mg of calcium carbonate per gram of silico- anhydrous aluminate and / or magnesium exchange kinetics of at least 60 mg of calcium carbonate per gram of anhydrous silico-aluminate after one minute of contact. 4. / Silico-aluminate according to the preceding claim, characterized in that it has a calcium exchange capacity of at least 270 mg of calcium carbonate per gram of anhydrous silico-aluminate, kinetics of calcium exchange at least 220 mg of calcium carbonate per gram of anhydrous silico-aluminate after one minute of contact, a magnesium exchange capacity of at least 190 mg of calcium carbonate per gram of anhydrous silico-aluminate and / or kinetics of magnesium exchange of at least 65 mg of calcium carbonate per gram of anhydrous silico-aluminate after one minute of contact. 5. / amorphous silico-aluminate according to any one of the preceding claims, characterized in that it has a specific surface of between 10 and 20 m2 / g and / or a pore volume of at least 2 cm3 / g, preferably at least 4 cm3 / g. 6. / amorphous silico-aluminate according to any one of the preceding claims, characterized in that it has an oil absorption of at least 190 ml / 100 g. 7. / A detergent composition comprising in particular as an absorbent and / or sensor for divalent cations a silico-aluminate of solid and amorphous alkali metal according to any one of the preceding claims. 8. / detergent composition according to the preceding claim, characterized in that the amount of silico-aluminate present is between 4 and 40% by weight of the detergent composition. 9. / A process for preparing the solid and amorphous alkali metal silico-aluminate according to any one of claims 1 to 6, characterized in that it comprises the following stages: (1) mixing an aqueous solution of silicate of alkali metal of SiO2 / M2O molar ratio greater than or equal to 2 and of dry extract of between 30 and 50% by weight with an aqueous solution of alkali metal aluminate diluted by addition of alkali metal hydroxide and water, so that the molar composition of the mixture before gelling is as follows:

2-2.9 SiO2: 0.8-1.2 Al2O3; 3-10 M2O; 60-200 H2O;

in which M represents an alkali metal, (2) possible maturing of the gel formed in step (1), (3) filtration or centrifugation, (4) washing, (5) drying of the suspension obtained after step (4 ) and (6) possible grinding of the dried product. 10./ Method according to the preceding claim, characterized in that the alkali metal is sodium. 11./ Method according to one of claims 9 and 10, characterized in that steps (1) and (2) are carried out with stirring. 12./ Method according to any one of claims 9 to 11, characterized in that the mixture before gelation has the following molar composition:

2 SiO2; 0.8-1.2 Al2O3; 4-8 M2O; 60-200 H2O.

13./ Method according to the preceding claim, characterized in that the mixture before gelation has the following molar composition:

2 SiO2; 1 Al2O3; 6 M2O; 120 H2O.

14./ Method according to any one of claims 9 to 13, characterized in that the mixing step (1) is carried out either by introducing the two aqueous solutions in parallel, or by introducing the aqueous silicate solution of alkali metal in the dilute aqueous solution of alkali metal aluminate. 15./ A method according to any one of claims 9 to 14, characterized in that the method is carried out at a temperature between 15 and 50 ° C, preferably at a temperature between 15 and 30 ° C. 16./ A method according to any one of claims 9 to 15, characterized in that following the gelling and possible ripening, one implements a carbonation of the product obtained. 17./ A method according to any one of claims 9 to 16, characterized in that additives are added in the suspension before the drying step (5), or optionally in the mixture of step (1). 18 / A method according to any one of claims 9 to 17, characterized in that the drying step (5) is carried out by atomization.